1. Field of the Invention
The present invention relates to a power supply for a tire pressure monitoring system, and more particularly, to a power supply for generating an electric source using a static magnetic field of a tire pressure monitoring system.
2. Description of the Related Art
In general, a tire pressure monitoring system (TPMS) measures a tire pressure, and generates an alarm and informs a user when the measured pressure is lower than a previously set reference pressure. The TPMS uses a general small-sized dry cell as an electric source. However, the small-sized dry cell has a different temperature characteristic depending on material or internal substance of the dry cell, and is still in existence of a possibility of deteriorating its performance at a high temperature and a low temperature.
Due to such a drawback of the electric source, a battery-less tire pressure monitoring system (TPMS) is under development. The battery-less TPMS wireless transmits external energy. As such a technology, there are a low frequency (LF) transmission method using a LF electromagnetic wave being an alternating electronic field and a radio frequency (RF) method using an ultra high frequency (UHF) electromagnetic wave. Both methods are based on the alternating electronic field where the electronic field is temporally changed in polarity. In the LF method, energy is transmitted using a magnetic field coupling method, and in the RF method, the energy is transmitted using an electronic field coupling method.
The battery-less tire pressure monitoring system employing the general methods includes a receiver and a transmitter. The receiver is installed at a car and is connected with a constituent element transmitting the energy. The transmitter is installed at a tire, and receives the energy from the energy transmitting element, uses the received energy as a driving power, measures the tire pressure, and transmits the measured tire pressure data to the receiver.
Since the transmitter using the LF and RF methods needs a electromagnetic wave source, it should include the constituent element, that is, a LF or RF antenna for transmitting the energy to a peripheral position of the tire, that is, to a periphery of the tire such as an inner side of a car fender, and should wire connect the LF or RF antenna with the receiver.
As described above, in the conventional tire pressure monitoring system, in case where the general dry cell is used, the temperature characteristic is different depending on the material and the internal substance of the dry cell and therefore, there is a drawback in that performance can be deteriorated depending on a temperature.
Further, the tire pressure monitoring system using the LF or RF method should be wire connected with the energy transmitting element and therefore, there is a drawback in that its installation at the car is difficult and its installation cost is expensive, thereby laying a burden on a user or manufacturer in purchasing or manufacturing the battery-less (that is, dry cell-less) tire pressure monitoring system.